The present invention relates to hoses and more particularly to flexible metal hosing constructed for transporting fluent substances.
Strip-wound flexible metal hosing has long been employed in materials handling applications where noxious gasses or particulate substances must be transported. This type of hosing is also commonly used for handling food products, such as grain, and plastics, where high purity must be maintained, as well as products of combustion. The fluent material is propelled through the hose by differential pressure applied across the length of the hose.
Original continuous ribbon designs inherently possessed significant disadvantages. The interconnecting ribbon edges had a tendency to part or unwrap during periods of stressful use, i.e., severe twisting, flexing, or during initial installation, particularly adjacent any circumferential cut location. Unwinding resulted in product loss, lost production time and repair costs. Further, when a hose wall did separate, a successful, lasting repair was extremely difficult to achieve. For these reasons, secondary reinforcement by the end user became conventional in the art. Reinforcement techniques include wrapping the hose with tape and physically crimping cut surfaces to prevent unwrapping. These steps added time, material expense, and labor cost.
U.S. Pat. No. 3,682,203 to Foti et al. (the ""203 patent), which is incorporated herein by reference in its entirety, discloses a flexible metal hose formed from a helically wound metal strip. The edges of adjacent convolutions, or turns, are deformed to interfold slidably so that adjoining convolutions slide axially against one another. This sliding action permits the hose to be flexed, or bent. In one conventional hose of this type, a plurality of mating projections and recessions prevent the sliding surfaces from moving in the helical direction, while allowing sliding in the axial direction when the hose is flexed. Hoses formed in accordance with the ""203 patent do not normally need any secondary reinforcement or special handling techniques during installation.
In the hose disclosed by the ""203 patent the mating projections and recessions were formed by serration patterns on mating surfaces of adjacent convolutions. Serrations in one surface physically engage serrations in an opposing surface, increasing the force required to unwind the strip in the helical direction while facilitating relative axial movement of the convolutions as the hose was flexed.
When fluent substances were transported through a hose constructed according to the ""203 patent, the application of differential pressure was often required to efficiently move the substance. The serrations formed leakage paths to or from the hose, making maintaining differential pressure difficult. The mass flow rate of gaseous or particulate substances decreased to such an extent that the basic hose was modified by sealing the hose interior from the ambient environment. One technique was to line the convolution junctures with a helical bead of packing material to block the leakage paths. Although this technique maintained a seal, the modified hose was costly to manufacture and, for that reason, expensive to purchase.
The present invention provides a new and improved flexible metal hose for use in transporting fluent materials, such as gases and particulate substances, wherein the hose is readily flexed without unwinding the convolutions yet effectively directs the fluent materials therethrough without requiring any packing materials.
In an illustrated embodiment of the present invention a flexible metal hose for use in transporting fluent substances is provided that is formed from a metal strip generally helically wound about a hose axis. The strip has a generally xe2x80x9cSxe2x80x9d shaped cross sectional configuration formed by axially spaced radially inner and outer body portions and opposite strip edges forming reversely curved radially outer and inner lips that extend from the respective body portions. The lips of adjacent convolutions are interfitted to provide a first surface on one convolution that undergoes sliding movement relative to a second surface of an adjoining convolution when the hose is flexed. The first and second surfaces have a plurality of projections and recessions that mesh to enable the surfaces to slide relative to each other generally parallel to the hose axis while substantially impeding relative sliding in directions not generally parallel to the hose axis. The first surface is disposed on one convolution lip and the second surface is formed on a body portion of the adjoining convolution. A third smooth surface, formed on the other convolution lip, is biased into sealing engagement with a conforming sealing surface. The sealing engagement between the third and conforming sealing surfaces extends continuously along the hose on a generally helical path for blocking leakage of fluent material between said first and second surfaces.
In one disclosed embodiment of the invention the third surface forms a radially outer face of the other lip and the conforming sealing surface forms a radially inner face of the confronting body portion of the adjoining convolution. The engaged sealing surfaces are interposed between the interior of the hose and the first and second surfaces.
In another embodiment, the flexible metal hose is a xe2x80x9csmooth borexe2x80x9d hose in that it includes a second generally helical strip wound with the first strip to provide a relatively smooth interior hose wall. The second strip comprises a first edge region curved about the hose axis and extending along the interior of the hose. A radially inner face of the first edge region forms the inner hose surface. A second edge region extends between adjoining convolutions of the first strip, with the conforming sealing surface formed on one radial face of the second edge region.
In this embodiment, the second edge region of the second strip defines an opposite face that sealingly engages the surrounding body portion of the first strip.
Further features and advantages of the invention will become apparent from the following detailed description of illustrated embodiments made with reference to the accompanying drawings.